1. Technology Field
The present invention generally relates to optical transceiver modules. In particular, the present invention relates to a system for securing an optical subassembly within an optical transceiver while still allowing for its interconnection with other transceiver components.
2. The Related Technology
Fiber optics technology is increasingly used for transmitting voice and data signals. As a transmission medium, light provides a number of advantages over traditional electrical communication techniques. For example, optical signals allow for extremely high transmission rates and very high bandwidth capabilities. Also, optical signals are resistant to electro-magnetic interferences that would otherwise interfere with electrical signals. Light also provides a more secure signal because it doesn't allow portions of the signal to escape from the fiber optic cable as can occur with electrical signals in wire-based systems. Light also can be conducted over greater distances without the signal loss typically associated with electrical signals on copper wire.
While optical communications provide a number of advantages, the use of light as a transmission medium presents a number of implementation challenges. In particular, the data carried by an optical signal must be converted to an electrical format when received by a device, such as a network switch. Conversely, when data is transmitted to the optical network, it must be converted from an electrical signal to an optical signal. A number of protocols define the conversion of electrical signals to optical signals and transmission of those optical, including the ANSI Fibre Channel (FC) protocol. The FC protocol is typically implemented using a transceiver module at both ends of a fiber optic cable. Each transceiver module typically contains a laser transmitter circuit capable of converting electrical signals to optical signals, and an optical receiver capable of converting received optical signals back into electrical signals.
Typically, a transceiver module is electrically interfaced with a host device—such as a host computer, switching hub, network router, switch box, computer I/O and the like—via a compatible connection port. Moreover, in some applications it is desirable to miniaturize the physical size of the transceiver module to increase the port density, and therefore accommodate a higher number of network connections within a given physical space. In addition, in many applications, it is desirable for the module to be hot-pluggable, which permits the module to be inserted and removed from the host system without removing electrical power. To accomplish many of these objectives, international and industry standards have been adopted that define the physical size and shape of optical transceiver modules to ensure compatibility between different manufacturers. For example, in 2000, a group of optical manufacturers developed a set of standards for optical transceiver modules called the Small Form-factor Pluggable (“SFP”) Transceiver Multi-Source Agreement (“MSA”), incorporated herein by reference. In addition to the details of the electrical interface, this standard defines the physical size and shape for the SFP transceiver modules, and the corresponding host port, so as to insure interoperability between different manufacturers' products. There have been several subsequent standards, and proposals for new standards, including the XFP MSA for 10 Gigabit per second modules using a serial electrical interface, that also define the form factors and connection standards for pluggable optoelectronic modules, such as the published draft version 0.92 (XFP MSA), incorporated herein by reference.
Regardless of the particular form factor employed, it is of common concern in the design of transceiver modules to interconnect components residing within the transceiver module securely and accurately, while at the same time preventing damage to the components during interconnection. By way of example an optical subassembly, such as a transmitter optical subassembly (“TOSA”) that houses a laser for the production of optical data signals, must form a secure electrical attachment to a printed circuit board (“PCB”) when the two components are included within an optical transceiver module (“transceiver”). Most often, this electrical interconnection is achieved via a plurality of electrical leads that extend from the TOSA and are each soldered to contact pads correspondingly positioned on the PCB. Such interconnection enables electrical data signals originating with a host device with which the optical transceiver module is operatively connected to be transferred from the PCB to the TOSA laser, where they are converted to an optical data signal.
Notwithstanding the secure connection that must be achieved between it and the PCB, the TOSA further includes a nosepiece that must be precisely positioned within a port of the transceiver to enable interconnection of the nosepiece with a connectorized optical fiber. Positioning of the TOSA during assembly must be such that the TOSA is properly positioned within the port while also acceptably oriented so as to enable connection of its leads with the PCB. However, know methods for facilitating such positioning and orientation are also apt to produce unreasonable amounts of stress or strain on the TOSA structure or on the TOSA-PCB lead interconnections themselves. If such stress and strain exceeds nominal limits, breakage or misalignment of the TOSA or the lead interconnections may occur, which can result in rejection of the component or entire transceiver if detected, or in sub-optimal subassembly performance if not detected.
In light of this, a need exists for an interconnection scheme between optical subassemblies and other components within a module, such as an optical transceiver module, that solves the above challenges while ensuring optimum performance of the module. In addition, the module should be implemented in a manner that meets existing standard form factors and does not interfere with other module components.